1. Field
The present invention relates to a method and a system for changing the power consumption value available for an HVAC (Heating Ventilation and Air Conditioning) unit of a vehicle when an available battery power for batteries of the vehicle is low and more particularly to a method and a system for non-linearly changing the power consumption value available for the HVAC unit when the available battery power decreases to a power value less than a low power value.
2. Description of the Related Art
In order to improve a user's experience and safety with a vehicle having rechargeable batteries, manufacturers have sought novel ways to enhance the operation of various units of the vehicle when the user is travelling with the vehicle with a low available battery power/state of charge. Because each of the various units of the vehicle require a certain power value for their operations, it is important to determine a power allocation for the units based on the needs of the user and the vehicle. A vehicle can incorporate an HVAC unit which controls the climate inside the vehicle and adjusts the environmental comfort for the user. An HVAC unit may also perform defogging/defrosting operations for windows of the vehicle depending on the vehicle's speed, humidity, temperature and other climate conditions. A vehicle generally decreases the power consumption value available for the HVAC unit and other devices of the vehicle by linear rates of power reduction relative to a reduction in the available battery power.
A drawback of linearly decreasing the power consumption value available for the HVAC unit has been that the power allocation to the HVAC unit may be insufficient because the HVAC unit may require a greater allocated power when the available battery power is low. For example, under cold or humid climate conditions, a sudden decrease in the power consumption value available for the HVAC unit may hinder the window defogging/defrosting operations of the HVAC unit which may be important for enhancing the field of vision of the user.
Another drawback of linearly decreasing the power consumption value available for the HVAC unit has been that the power allocation to the HVAC unit may be inefficient because the HVAC unit may require less power than the allocated power consumption value. For example, under ideal climate conditions and a low vehicle speed, the HVAC unit may require less power than the power consumption value allocated under the linear reduction method or system. The inefficient allocation of power may hinder the operation of the vehicle given that other devices of the vehicle could have used the unnecessary power allocated to the HVAC unit.
Thus, there is a need for a method and a system directed to changing the power consumption value available for an HVAC unit of a vehicle when an available battery power is low and more particularly to a method and a system for non-linearly changing the power consumption value available for the HVAC unit when the available battery power decreases to a power value less than a low power value. There is also a need for a method and a system directed to decreasing the power consumption value available for an HVAC unit by an initial slow rate for avoiding a sudden or abrupt reduction in the power available for the HVAC unit.